package com.ctrip.apollo.core.utils;

 import org.slf4j.Logger;

 import org.slf4j.LoggerFactory;

 import java.net.NetworkInterface;

 import java.nio.BufferUnderflowException;

 import java.nio.ByteBuffer;

 import java.security.SecureRandom;

 import java.util.Enumeration;

 /**

  * @author Jason Song(song_s@ctrip.com)

  */

 public class MachineUtil {

   private static final Logger logger = LoggerFactory.getLogger(MachineUtil.class);

   private static final int MACHINE_IDENTIFIER = createMachineIdentifier();

   public static int getMachineIdentifier() {

     return MACHINE_IDENTIFIER;

   }

   /**

    * Get the machine identifier from mac address

    *

    * @see <a href=https://github.com/mongodb/mongo-java-driver/blob/master/bson/src/main/org/bson/types/ObjectId.java>ObjectId.java</a>

    */

   private static int createMachineIdentifier() {

     // build a 2-byte machine piece based on NICs info

     int machinePiece;

     try {

       StringBuilder sb = new StringBuilder();

       Enumeration<NetworkInterface> e = NetworkInterface.getNetworkInterfaces();

       while (e.hasMoreElements()) {

         NetworkInterface ni = e.nextElement();

         sb.append(ni.toString());

         byte[] mac = ni.getHardwareAddress();

         if (mac != null) {

           ByteBuffer bb = ByteBuffer.wrap(mac);

           try {

             sb.append(bb.getChar());

             sb.append(bb.getChar());

             sb.append(bb.getChar());

           } catch (BufferUnderflowException shortHardwareAddressException) { //NOPMD

             // mac with less than 6 bytes. continue

           }

         }

       }

       machinePiece = sb.toString().hashCode();

     } catch (Throwable ex) {

       // exception sometimes happens with IBM JVM, use random

       machinePiece = (new SecureRandom().nextInt());

       logger.warn(

           "Failed to get machine identifier from network interface, using random number instead",

           ex);

     }

     return machinePiece;

   }

 }